The present invention relates to a stroke self-adjusting mechanism for a control cable, and more particularly to a mechanism for remotely operating a working device through the control cable by an operating device such as lever in vehicle, or the like.
The control cable consists essentially of a flexible conduit and a flexible inner cable slidably inserted into the conduit. The conduit is mounted on the vehicle body by fittings provided to the both ends thereof, and the tension load added to the one end of the inner cable in the operating side is transmitted to the working device connected to the other end of the inner cable.
The inner cable consists of a strand of hard-steel wires, and in a motor vehicle, is used for the remote control in clutch, brake or accelerator. However, especially in the clutch and the brake mechanisms, the inner cable cannot avoid causing expansion or slack gradually due to repeating of push-pull operations under the heavy tension. Therefore, since the smooth operations of the clutch and brake are inhibited, the inner cable should be adjusted by an adjusting screw or the like as occasion demands. However, such an adjustment of the inner cable is very inconvenient in handling. Thus, it is desirable to adjust automatically the inner cable.
In the clutch mechanism in the vehicle, when a clutch plate is worn, a clutch release lever contacts strongly with a clutch release bearing, and then pushes a clutch operating fork. As a result, the inner cable is pulled as if the inner cable shrinks. In that case, though it is also required to adjust the inner cable by the adjusting screw or the like, the adjustment with the screw is very inconvenient.
A few suggestions of the stroke self-adjusting mechanism has been made in order to exclude the disadvantages described above. However, all the mechanisms suggested are those for applied to only the expansion or slack of the inner cable. For example, U.S. Pat. No. 3,621,959 discloses a self-adjusting clutch release mechanism comprising a ratchet member pivotally connected to a clutch pedal and connected to the inner cable, and a pawl pivotally connected to the pedal and engaging with the ratchet member. The pawl disengages from the ratchet member when the pedal is held against the stop. Thus, a spring connected to the ratchet member takes up the expansion or slack of the inner cable automatically. However, the mechanism suggested is very complex. Especially, if ratchet teeth which can carry out the micro-adjustment are employed, they cannot endure in the heavy load, and on the other hand, if ratchet teeth which can endure the heavy load are employed, they result in rough-adjustment. In addition, the mechanism suggested in unsatisfied in the stroke adjustment of the inner cable. Also, when the vehicle is running, the distance of both fitting positions for connecting both ends of the conduit is slightly variable due to any strain of the vehicle body. As a result, the inner cable shows apparent expansion and contraction as if the inner cable itself is expanded and contracted. Especially, the apparent expansion results in functioning the self-adjusting mechanism. For example, in the clutch mechanism, the apparent expansion keeps the clutch plate to the incompletely clutched state while the vehicle is running, finally causing burning damages of the clutch plate, and in the brake mechanism, the apparent expansion keeps the brake to the working state, due to absorbing and adjusting the apparent expansion automatically in the similar manner to the clutch, finally causing burning damages of a brake lining. Furthermore, it is impossible that the contraction of the inner cable as described above is adjusted by the coventional self-adjusting mechanism.